The normal heart rhythm is slightly irregular. Generally, normal irregularity of the heart's rhythm reflects the permanent adaptation of the human body to the environment. In this context the first sign of an impaired heart rhythm is either a persistent increase or a persistent decrease in the variability of the heart's rhythm. Sometimes the change in the heart's rhythm alternates between increases and decreases in the variability of the heart's rhythm, and vice versa. Prolonged increases, or decreases, and combinations thereof, can lead to cardiac ectopic events ranging from non-sustained ventricular tachycardia to cardiac arrest.
It is believed the variability of the heart's rhythm is controlled by two branches of the autonomic nervous system; the sympathetic branch and the parasympathetic branch. The sympathetic branch increases the heart rate. Its prime function is to prepare the body for stress, the so-called "fight or flight response". The parasympathetic branch decreases the heart rate as when eating or sleeping.
In the Soviet Union, Rhythmography, that is the study of normal and abnormal variations in heart rhythm, was utilized extensively to determine the condition of individuals and their stress state. This was particularly true of cosmonauts. It was determined for example, that the heart rate variability of a conditioned athlete is much greater than that of person with coronary disease, that is the histogram of heart rate variation of a well conditioned athlete exhibits a broad range of variability in the Time Intervals between heart beats and a low relative Amplitude of the Mode. That is the highest number of Time Intervals recorded in a series of Time Intervals. The histogram of a person with a coronary disease exhibits a narrow range of variability and a high relative Amplitude of the Mode, that is the peak of the histogram.
Applicant, Boris Golosarsky, previously received two patents in the Soviet Union, namely; SU-1683679 for an apparatus, which enables a physician to determine the arithmetic Mean, the Mode, the relative Amplitude of the Mode, and the range of variability of a subject. In the second patent in the Soviet Union, SU-1769894, he disclosed how these measurements may be utilized together with electrosleep to treat post myocardial infarction e.g. heart attack patients.
Polar Electro Oy of Finland has a patented apparatus comprised of a chest strap with a two lead ECO signal sensor and transmitter, which transmits the heart beat Time Intervals to a wrist mounted unit that can be conveniently used in this invention. See U.S. Pat. Nos. 4,625,733, D278,746, and D287,403.
Pulse sensors of various types may also be used to detect the Time Interval between heart beats, (Start-of-Systole to Start-of-Systole, SOS), is essentially equal to the Time Interval between RR peaks in an electrocardiogram, (ECG).